A control device of a vehicle drive device is well known that includes an electric motor as a drive power source for running as is commonly seen in hybrid vehicles and electric vehicles. For example, this corresponds to a control device of a vehicle drive device of Patent Document 1.
The vehicle drive device of Patent Document 1 includes an engine outputting power to drive wheels, a first electric motor generating electricity from a portion of the output power of the engine, and a second electric motor capable of input/output of power from/to the drive wheels. The control device of the vehicle drive device limits a required torque to be output to an output rotating member of the vehicle drive device to a lower level in a high rotation speed region of the second electric motor as a second electric is motor rotation speed increases, so as to prevent higher rotation of the second electric motor and suppress overcharge of an electric-motor power source (battery). Specifically, in the limitation of the required torque, as depicted in FIG. 7 of Patent Document 1, a required torque limit value is set in advance to be reduced at a certain reduction rate relative to an increase in the second electric motor rotation speed and the required torque is limited by determining the required torque so as not to exceed the required torque limit value.
Patent Document 2 discloses a technique of limiting an output torque of a second electric motor (hereinafter referred to as a second electric motor torque) in a vehicle drive device including an engine outputting power to drive wheels, a first electric motor that is an electric generator generating electricity from a portion of the output of the engine, and the second electric motor that is a motor capable of input/output of power from/to the drive wheels. Although the control device of the vehicle drive device described in Patent Document 2 limits the second electric motor torque toward zero at the time of slip of the drive wheels, a reduced amount per unit time of the second electric is motor torque (hereinafter referred to as an MG torque limiting slope) is variable depending on a charge limitation state of a battery and a level of electric power generation of the first electric motor. As a result, a temporarily high voltage on the input side of the electric motors is suppressed to protect a high power system circuit for supplying elect is power to the first electric motor and the second electric motor.